1. Field
This disclosure generally relates to the field of display configurations. More particularly, the disclosure relates to high speed projector configurations.
2. General Background
Several current display configurations require high frame rate color projection. For example, temporally multiplexed multilayered volumetric displays and multiview autosteroscopic displays typically require high frame rate color projection. The faster display allows for more layers or views to be displayed. Accordingly, the displayed three-dimensional (“3-D”) volume is displayed with more layers and appears smoother with a high frame rate color projection than a slow frame rate color projection. Similarly, a 3-D multiscopic image is displayed with more views and appears to have smoother parallax and supports a greater depth. Projection panning and smooth action replay, e.g., as necessitated by sporting videos and action movies, are other examples that also typically require high frame rate color projection. Current projectors are capable of operating at one hundred twenty Hertz, which is simply not fast enough to produce the high quality display required for these various display configurations. Although current projectors may be rapid enough for 3D stereoscopic projection, the frame rate limits the number of layers in the volumetric display, the number of views in 3-D multiscopic displays, the panning speed in the panned projection, and the apparent fluidity of fast action motion.
Prior to digital projection, film strip projectors and CRTs were utilized for high frame rate applications. As consumer needs are now directed to digital applications, film strip projectors and CRTs cannot provide high frame rates for those consumer needs.
Current high speed projection systems typically utilize a fixed film sequence and are cumbersome for long run times. Further, new media is typically difficult to utilize and update with the current high speed projection systems. When high speed binary projectors are utilized in multi-view 3D displays, greyscale is usually approximated utilizing spatial dithering of binary pixels. The spatial dithering reduces the resolution of the image and introduces artifacts. Further, many current projection systems, e.g., Digital Micromirror Devices (“DMDs”), utilize temporal multiplexing for time sequential luminance and color. Such projection systems are incompatible with the volumetric display, panned projection, and fast action motion configurations because the time sequential colors and/or luminance become separated. As a result, the time sequential colors and/or luminance appear as separate layers or rainbow smear artifacts.
Current Light Emitting Diode (“LED”) displays can be modulated quickly, e.g., at greater than ten kilohertz, but are typically quite large, e.g., stadium displays, or quite small, e.g., Organic Light Emitting Diode (“OLED”) microdisplays. Further, LED displays typically run at common slow frame rates, e.g., sixty Hertz or one hundred twenty Hertz, at least partially because LEDs rely on pulse width modulation (“PWM”) to control pixel luminance, i.e., brightness. LEDs are driven with a constant voltage and have a luminance varied with PWM, e.g., the LEDs are turned on and off at different duty cycles, since the LED luminance is nonlinear with voltage and direct current control is too expensive and cumbersome.
Another current approach has a volumetric display utilizing a rim-driven varifocal mirror and high speed digital light processing (“DLP”) backlit liquid crystal display (“LCD”) panel. A high speed DMD projector is utilized as a pixel-level backlight to selectively backlight portions of a slow frame rate LCD panel. The varifocal mirror places sections of the LCD image at different planes to provide two and one half dimensional, e.g., extruded, volumetric imagery. Only one image is shown on the LCD panel at a time and only portions of that image are selectively backlit in sequence by the high-speed projector. Those partial images never overlap. Each color voxel in the volumetric display is given a single depth or multiple depths, but all depths must be the same color. The layers are not independent. As a result, the holes in the layers become apparent to a user viewing the display off-axis, e.g., not directly in front of the display. The high speed projector and LCD must be aligned pixel for pixel. Accordingly, the combination of the high speed projector is not scalable to multiple LCDs and projectors for higher resolution, speed, and/or luminance. The volumetric display's single LCD image with high speed projector backlight is also not compatible with panned projection and smooth action replay as multiple high speed image frames are not provided. A single image whose sections are sequentially lit in rapid order is only provided.
Therefore, current projection systems do not provide adequate image quality for particular projection applications. A high speed full color projection system that projects at a frame rate of at least one thousand frames per second without reliance on luminance and color generation through temporal multiplexing is needed for a variety of projection applications, e.g., volumetric display, panned projection, and fast action motion configurations.